Bottom Line:
Upon functionalization by -NH2 or -CH3 group, the steric hindrance in MIL-101 increases; consequently, the interactions between glucose and framework become less attractive, thus reducing the capacity and mobility of glucose.The presence of ionic liquid, 1-ethyl-3-methyl-imidazolium acetate, as an impurity reduces the strength of hydrogen-bonding between glucose and MIL-101, and leads to lower capacity and mobility.Upon adding anti-solvent (ethanol or acetone), a similar adverse effect is observed.

Affiliation: Department of Chemical and Biomolecular Engineering, National University of Singapore, 117576, Singapore.

ABSTRACTA molecular simulation study is reported on glucose recovery from aqueous solutions by adsorption in metal-organic framework MIL-101. The F atom of MIL-101 is identified to be the most favorable adsorption site. Among three MIL-101-X (X = H, NH2 or CH3), the parent MIL-101 exhibits the highest adsorption capacity and recovery efficacy. Upon functionalization by -NH2 or -CH3 group, the steric hindrance in MIL-101 increases; consequently, the interactions between glucose and framework become less attractive, thus reducing the capacity and mobility of glucose. The presence of ionic liquid, 1-ethyl-3-methyl-imidazolium acetate, as an impurity reduces the strength of hydrogen-bonding between glucose and MIL-101, and leads to lower capacity and mobility. Upon adding anti-solvent (ethanol or acetone), a similar adverse effect is observed. The simulation study provides useful structural and dynamic properties of glucose in MIL-101, and it suggests that MIL-101 might be a potential candidate for glucose recovery.

Mentions:
where r is the distance between atoms i and j, is the number of atom j around i within a shell from r to r + Δr, V is the system volume, Ni and Nj are the numbers of atoms i and j, respectively. Figure 3 shows the g(r) between the Hg atom of glucose and the F, C3, and O2 atoms of MIL-101. No peak is observed around the C3 and O2 atoms; in contrast, there is a pronounced peak at r = 1.8 Å around the F atom. This suggests the F atom, due to its high electronegativity, is the most favorable site for glucose adsorption. Indeed, a hydrogen-bond (H-bond) is formed between the F atom and glucose as evidenced by two geometrical criteria: (1) the distance between a donor and an acceptor ≤ 0.35 nm and (2) the angle of hydrogen-donor-acceptor (between hydrogen-donor and donor-acceptor) ≤ 30° 2829. In glucose/water/MIL-101 system, the number of H-bonds between all the adsorbed glucose molecules and MIL-101 was estimated to be 58.3.

Mentions:
where r is the distance between atoms i and j, is the number of atom j around i within a shell from r to r + Δr, V is the system volume, Ni and Nj are the numbers of atoms i and j, respectively. Figure 3 shows the g(r) between the Hg atom of glucose and the F, C3, and O2 atoms of MIL-101. No peak is observed around the C3 and O2 atoms; in contrast, there is a pronounced peak at r = 1.8 Å around the F atom. This suggests the F atom, due to its high electronegativity, is the most favorable site for glucose adsorption. Indeed, a hydrogen-bond (H-bond) is formed between the F atom and glucose as evidenced by two geometrical criteria: (1) the distance between a donor and an acceptor ≤ 0.35 nm and (2) the angle of hydrogen-donor-acceptor (between hydrogen-donor and donor-acceptor) ≤ 30° 2829. In glucose/water/MIL-101 system, the number of H-bonds between all the adsorbed glucose molecules and MIL-101 was estimated to be 58.3.

Bottom Line:
Upon functionalization by -NH2 or -CH3 group, the steric hindrance in MIL-101 increases; consequently, the interactions between glucose and framework become less attractive, thus reducing the capacity and mobility of glucose.The presence of ionic liquid, 1-ethyl-3-methyl-imidazolium acetate, as an impurity reduces the strength of hydrogen-bonding between glucose and MIL-101, and leads to lower capacity and mobility.Upon adding anti-solvent (ethanol or acetone), a similar adverse effect is observed.

Affiliation:
Department of Chemical and Biomolecular Engineering, National University of Singapore, 117576, Singapore.

ABSTRACTA molecular simulation study is reported on glucose recovery from aqueous solutions by adsorption in metal-organic framework MIL-101. The F atom of MIL-101 is identified to be the most favorable adsorption site. Among three MIL-101-X (X = H, NH2 or CH3), the parent MIL-101 exhibits the highest adsorption capacity and recovery efficacy. Upon functionalization by -NH2 or -CH3 group, the steric hindrance in MIL-101 increases; consequently, the interactions between glucose and framework become less attractive, thus reducing the capacity and mobility of glucose. The presence of ionic liquid, 1-ethyl-3-methyl-imidazolium acetate, as an impurity reduces the strength of hydrogen-bonding between glucose and MIL-101, and leads to lower capacity and mobility. Upon adding anti-solvent (ethanol or acetone), a similar adverse effect is observed. The simulation study provides useful structural and dynamic properties of glucose in MIL-101, and it suggests that MIL-101 might be a potential candidate for glucose recovery.